How Much Friction is Desirable

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    Friction
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Discussion Overview

The discussion revolves around the desirable amount of friction for a car with four wheels on a surface, specifically focusing on the balance between too much and too little friction. Participants explore the implications of friction on performance, particularly in the context of a 1 kg toy car on a wooden surface.

Discussion Character

  • Exploratory
  • Technical explanation
  • Debate/contested
  • Conceptual clarification

Main Points Raised

  • Some participants suggest that too much friction can slow the car down, while too little can lead to slipping.
  • Others argue that rolling resistance is a more significant factor than friction, particularly unless tire surfaces behave like adhesives.
  • It is noted that rubber tires experience significant loss due to friction with the road, primarily due to constant distortion and tread scuffing.
  • Some participants mention that steel wheels on steel rails are more efficient due to reduced contact area and distortion, but static friction limits acceleration.
  • One participant proposes that rubber tires should suffice for a 1 kg toy car, suggesting that optimization requires specific information about acceleration and top speed.
  • There is a discussion about the role of internal losses in rubber tires, with some stating that hysteresis contributes more to energy loss than scuffing.
  • Another participant raises the idea of optimizing static friction while minimizing undesirable friction forces.

Areas of Agreement / Disagreement

Participants express differing views on the role and impact of friction and rolling resistance, indicating that multiple competing perspectives remain without a clear consensus on the optimal amount of friction.

Contextual Notes

Some discussions involve assumptions about the specific conditions of the car's operation, such as acceleration and top speed, which may influence the analysis of friction and rolling resistance.

Sidelines
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Given a set of wheels connected with a frame and chassis (a typical car), on a surface, how much friction is desirable? Too much friction would slow the car down, where as too little would cause slipping.
A specific example would be four equal wheels with a frame and body, around 1 kg on a wooden surface.
 
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Sidelines said:
Too much friction would slow the car down ...
Rolling resistance slows a car. Friction should not be much of a factor (unless tire surfaces start to act as adhesives). Wiki article:

http://en.wikipedia.org/wiki/Rolling_resistance
 
rcgldr said:
Rolling resistance slows a car. Friction should not be much of a factor (unless tire surfaces start to act as adhesives). Wiki article:

http://en.wikipedia.org/wiki/Rolling_resistance

With rubber tyres, there is a significant loss due to friction with the road because the tyre is constantly distorting as it comes in contact with the ground and the tread pattern 'scuffs'.
Steel wheels on steel rails are a lot more efficient as the contact area and the distortion are reduced but the low (static) friction limits acceleration (+ and -).
 
You are probably overthinking it. Rubber tires should do fine for a 1kg toy car. If it is important to optimize it, you need specific information about the acceleration and top speed of the car.
 
Khashishi said:
You are probably overthinking it. Rubber tires should do fine for a 1kg toy car. If it is important to optimize it, you need specific information about the acceleration and top speed of the car.

What, on PF? This is angels on a pinhead land.
 
sophiecentaur said:
With rubber tyres ... high rolling resistance.
Relatively stiff rubber tires, either very high perssure, or solid rubber tires, reduce rolling resistance, but generally have less grip.
 
sophiecentaur said:
With rubber tyres, there is a significant loss due to friction with the road because the tyre is constantly distorting as it comes in contact with the ground and the tread pattern 'scuffs'.
Actually most of the resistance is internal due to hysteresis of the rubber; not much scuffing going on.
 
I was thinking in terms of wear as being evidence of scuffing but I guess that is only a small fraction of the contribution to the heating up of the tyres due to internal losses when traveling (a good indicator of energy loss).
 
Sidelines said:
Too much friction would slow the car down, where as too little would cause slipping.
sliding friction / aerodynamic friction / tire deformation : BAD (creates resistance)
static friction : GOOD (provides traction)
 
  • #10
How could I optimize static friction in tires and downscale the bad friction forces?
This is more for thought than actual results if the whole 1 kg car seemed pointless.
 

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